1. Field of the Invention
The present invention relates to opthalmology and more particularly to artificial lenses used to restore binocular vision in aphakia.
2. Discussion of the Prior Art
Properly constructed artificial intraocular lenses are known to produce stable retinal images when placed in the eye. A major problem of intraocular lens implantation is the fixation of the lens in, in front of, or behind the pupillary aperture. In the prior art Flom U.S. Pat. No. 3,866,249 uses lenses with prongs, Potthast U.S. Pat. No. 3,913,148, and Richards and Grolman U.S. Pat. No. 3,925,825, use clips, Fedorov U.S. Pat. No. 3,673,616 and Binkhorst, use loops, Deitrick U.S. Pat. No. 3,711,870 uses suturing and Otter U.S. Pat. No. 3,906,551 and Krasnov U.S. Pat No. 3,922,728 employ combinations of the above. These devices have been unsatisfactory from a variety of standpoints, mostly related to difficulty with fixation in the eye without causing damage to the ocular structures.
The fibrous sclera of the eye is the most suitable structure of the eye from which to support a plastic lens implant. The only place where the sclera presents itself inside the eye where it is accessible for fixation is the "scleral spur", an annular ring of sclera near the area where the iris and cornea meet. This area is called "the angle" (of the anterior chamber). Fixation to the scleral spur produces pure and stable scleral fixation.
Most of the lenses noted above are fixed to the iris or to remnants of the lens capsule left behind when a cataract is removed. The iris is a flimsy, vascular, mobile structure. Fixation of the plastic lens implant to the iris or lens capsule by means of sutures, loops, clips, scar tissue, etc., leaves a lens which is still mobile and capable of damaging the adjacent, delicate ocular structures.
Dr. Peter Choyce of London provided a lens in which a support system is contoured to fit in the angle against the scleral spur without appendages or suturing. Dr. Choyce's lenses eliminate some of the aforementioned problems. However, the Choyce lens introduces inherent problems caused by the various positioning mechanisms. Its biconcave, posteriorly placed optic does not allow for clearance of the iris beneath the lens. This contact of the iris with the lens blocks the normal flow of fluid in the eye, resulting in increased intraocular pressure (acute glaucoma). This requires more surgery to alleviate the glaucoma. West German Pat. No. 959,314 discloses a lens similar in some respects to the Choyce lens.
Accordingly, the present invention, is an improvement over the Choyce lens and obviates the need for prongs, loops, clips, incisions, and sutures, and most importantly moves the optical lens structure anteriorly in the eye with the object of prevention of glaucoma caused by contact of the lens posterior with the iris.
The optical lens structure is anteriorly convex with the posterior surface being either planar or convex. Binkhorst, 6 Ophthalmic Surgery 17 (1975) teaches that an optical lens structure, wherein the posterior surface is planar, is superior to other configurations. Thus, a planar posterior surface is the preferred embodiment.